PPL_D:YEAR:YEAR

URL: https://io.apps.fao.org/geoserver/wms/WPOP/WPOP_D/v2?service=WMS&version=1.3.0&request=GetCapabilities

From the dataset abstract

Estimated density of people per grid-cell, approximately 1km (0.008333 degrees) resolution. The units are number of people per Km² per pixel, expressed as unit: "ppl/Km²". The...

Source: Human Population Density (Global - Annual - 1 km)